Template:27
Unexpected use of template {{27}} - see Template:27 for details.
Template documentationTemplates {{1}}, {{2}}, {{3}}, etc. warn readers/editors that a typo exists in the page they are reading/editing. If {{27}} is called, you probably meant the parameter 27 (as {{{27}}} with triple braces), but in fact only double braces were used, invoking {{27}}. In addition to a warning, it also adds pages to Category:Templates with incorrect parameter syntax. For more information on how template parameters work, see mw:Help:Templates#Parameters.
However, the most problems have been caused by omitting the first brace "{" of a parameter and getting {{27}}}, as invoking Template:27 +"}" rather than parameter 27. This can be an insidious problem, especially when the transclusion of Template:27 is hidden, so that the effect is invisible to the person editing a page. For that reason, Template:27 now issues a warning to the user.
With that warning, the prior invisible access to Template:27 can now be understood to be a formerly unseen problem coded within a page.
- Note: this will also pick up several variations such as {{27|}} for {{{27|}}} and {{{27}}.
Periodically, people check what-links-here to see if anyone has accidentally invoked Template:27.